GB2324735A

GB2324735A - Cuff for a tracheal tube

Info

Publication number: GB2324735A
Application number: GB9808351A
Authority: GB
Inventors: George Downward; Peter Jeffrey Young
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-04-28
Filing date: 1998-04-21
Publication date: 1998-11-04
Anticipated expiration: 2018-04-21
Also published as: GB2324735B; GB9808351D0

Abstract

A tracheal cuff for preventing leakage of fluid from the subglottis into the trachea, which when deflated has a lesser diameter than that of the smallest expected tracheal diameter and when inflated the cuff walls are at stretch and a full circumference of the cuff wall comes into contact with the wall of the trachea thereby eliminating longitudinal folds in the cuff. The inflation characteristics of the cuff material enable the lateral tracheal wall pressure to be inferred.

Description

A DEVICE TO SEAL THE TRACHEA IN THE INTUBATED PATIENT The invention relates to a cuff of a tracheal tube which seals the trachea in the intubated patient.

The invention relates to a cuff on an endotracheal, tracheostomy, or endobronchial tube, for adult or paediatric use. The object of the invention is to prevent the passage of material from the subglottis and larynx and above, to the lungs, and to prevent the leakage of gas from the lungs, with an acceptable level of injury to the tracheal wall.

1. Current cuff devices, for endotracheal and tracheostomy tubes, are either high volume low pressure (HVLP), or low volume high pressure (LVH P).

1.1 HVLP cuffs do not seal against material passing across the cuff in all circumstances of use, due to longitudinal folds which form in the cuff material on inflation of the cuff in the trachea.

1.2 LVHP cuffs do seal, but have high potential for damage to tracheal mucosa, and are not acceptable for long term use.

2.The invention is a cuff which, when deflated, has a lesser diameter than that of the smallest expected tracheal diameter in the patient population for which the tube is designed.

2.1 Critically, the walls of the cuff will be at stretch on contact with the wall of the trachea, for a full circumference of the cuff, thereby eliminating the longitudinal folds that exist with HVLP cuffs.

2.2 Damage to the tracheal mucosa is minimised, as at a single intracuff pressure within the trachea, the lateral wall pressure does not exceed the accepted maximal pressure.( presently 30 cmH20 ), over the range of expected tracheal diameters in the patient population for which the tube is designed.

2.2.1 This can be achieved by constructing the cuff of a material such that, on inflation outside the trachea, the intracuff pressure remains constant (at a plateau pressure) over the expected range of tracheal diameters in the patient population for which the tube is designed (1.5 - 2.5 cm in adults; age adjusted in children). Hence the lateral pressure on the tracheal mucosa can be raised to a predictable and safe level, by raising the intracuff pressure of the device within the trachea to a pressure greater than, but no more than 30 cmH20 above the plateau pressure of the cuff, thereby creating a seal. This can be achieved with a standard pressure inflation device, or a cuff inflator and a pressure gauge.

3.The cuff shall be constructed out of any medical grade material which meets the required physical characteristics.

3.1 The ideal material is one which will plateau at a low pressure when in its cuff format. The ideal plateau is totally flat and is less than 120 cmH20 intracuff pressure when inflated out of the trachea.

3.2 Materials which, when in a cuff format, produce a higher plateau pressure can also be utilised, and will also provide adequately low tracheal wall pressure, as the wall pressure is a function of the plateau and intracuff pressure at seal, and not the plateau pressure itself.

3.3 Materials which, when in a cuff format, have a sloping plateau within 0 to 30 cmH20 over the expected range of tracheal diameters, would be acceptable, but the flatter the slope the better.

3.4 Prototype cuffs of thinly dipped latex have been made to have the correct characteristics when constructed as in 4 below. Silicone has also been used.

4.The cuff can be one of a variety of shapes, provided the walls of the cuff are at stretch on contact with the tracheal wall, for a full circumference, for a portion of its length, and that at a standard intracuff pressure the tracheal wall pressure is within recommended limits for all expected tracheal diameters. Two examples are described.

4.1 A cuff of resting diameter equal to the outside diameter of the endotracheal tube ie. zero volume at rest. Depending on the characteristics of the material, prestretching a straight or shaped cuff longitudinally may be necessary to achieve the inflation characteristics as in 2.2.1 or 3..

4.2 A preformed cuff of any shape, of lesser resting diameter than the trachea with the correct inflation characteristics, as in 2.2.1 or 3.

Fig 1 is a pressure (P) - volume (\/) curve for the cuff in 2.2.1 inflated outside the trachea.

Fig 2 is a pressure (P) - volume (V) curve for the cuff in 2.2.1 inflated inside the trachea. B minus A is less than 30.

Fig 3 is a pressure (P) - volume (\/) curve for the cuff in 3.3 inflated outside the trachea. A is less than 30 cmH2O.

Fig 4 is a pressure (P) - volume (V) curve for the cuff in 1.1 inflated outside the trachea. A is much greater than 30 cmH20.

Fig 5 is a pressure (P) - volume (V) curve for the cuff in 1.2 inflated outside the trachea. A equals 0.

A is the plateau pressure, and B is the pressure to which the cuff is inflated when in the trachea. C is the volume that has been added to the cuff when the cuff diameter reaches the smallest expected tracheal diameter, and D is the volume that has been added to the cuff when the cuff diameter reaches the largest expected tracheal diameter. Line W represents the tracheal wall pressure. T is the cuff volume on contact with the trachea.

Fig 6 is the complete device comprising of the tube 1, a standard cuff inflation port 2, and a cuff bonded to the tube shown inflated.

Claims

1 The invention is a cuff which, when deflated, has a lesser diameter than that of the smallest expected tracheal diameter in the patient population for which the tube is designed.

Critically, the walls of the cuff will be at stretch on contact with the wall of the trachea, for a full circumference of the cuff, thereby eliminating the longitudinal folds within the cuff.

The lateral tracheal wall pressure can be directly inferred from the intracuff pressure due to its inflation characteristics.

This device prevents leakage of fluid from the subglottis and above to the trachea whilst maintaining the ability to infer and control tracheal wall pressures.

2 The tracheal tube cuff as claimed in Claim 1 wherein damage to the tracheal mucosa is minimised, as at a single intracuff pressure within the trachea, the lateral wall pressure does not exceed the accepted maximal pressure ( presently 30 cmH20 ), over the range of expected tracheal diameters in the patient population for which the tube is designed.

This is achieved by constructing the cuff of a material such that, on inflation outside the trachea, the intracuff pressure remains nearly constant (at a plateau pressure) over the expected range of tracheal diameters in the patient population for which the tube is designed (1.5 - 2.5 cm in adults; age adjusted in children). Hence the lateral pressure on the tracheal mucosa can be raised to a predictable and safe level, by raising the intracuff pressure of the device within the trachea to a pressure greater than, but no more than a safe pressure above the plateau pressure of the cuff, thereby creating a seal. This can be achieved with a standard pressure inflation device, or a cuff inflator and a pressure gauge.

Amendments to the claims have been filed as follows CLAIMS 1. The invention is an elastic tracheal tube cuff which can be inflated to a constant pressure within a trachea such that the lateral wall pressure transmitted to the trachea does not exceed the accepted maximal recommended pressure (presently 30 cmH20 ), over the range of expected tracheal diameters in the patient population for which the tube is designed.

This is achieved by constructing the cuff of a material such that, on inflation outside the trachea, the intracuff pressure remains nearly constant (at a plateau pressure) over the expected range of tracheal diameters in the patient population for which the tube is designed (1.5 - 2.5 cm in adults; age adjusted in children).

Hence, when inflated inside the trachea, the lateral pressure on the tracheal wall can be raised to a predictable and safe level, by raising the intracuff pressure of the device to a pressure greater than, but no more than a safe pressure above the plateau pressure of the cuff, thereby creating a seal.